In female rats the medial preoptic area (MPOA) initiates a cyclic release of adenohypophyseal gonadotropins through a neurovascular mechanism involving the possible interplay of hypothalamic neurons, glial cells, cerebral spinal fluid (CSF), biogenic amines and hypophysiotrophic hormones. It is the purpose of this research to investigate some facets of these interactions. The basal diencephalon of female rats will be exposed by a parapharyngeal approach which will permit direct visualization of the hypophyseal portal vasculature, the median eminence, the optic chiasm and the optic nerves. Radioimmunoassay procedures will be employed to analyze gonadotropin concentrations in peripheral plasma. Using these preparations, the roles of various biogenic amines will be investigated by modifying the amine content within specific hypothalamic regions prior to MPOA electrochemical stimulation. The second major study to be pursued focuses upon the possibility that MPOA stimulation provokes a release of chemical substances into the CSF of the third ventricle to be transported to the median eminence and portal vasculature. To evalute this idea, CSF will be collected from MPOA stimulated rats and then tested for the presence of gonadotropin releasing substances. In addition to examining the relationship among MPOA, CSF and biogenic amines, the possible existance of intrahypothalamic fiber connections between the MPOA and the optic chiasm, the ventromedial nucleus and the suprachiasmatic nucleus will be explored. In these studies a specific hypothalamic region will be surgically isolated from the MPOA.